The present invention relates to apparatus for mounting a spray tank or container upon a tractor and, more particular, to a new structure for mounting such tank or container upon a tractor by means of a lifting hitch of the tractor.
Agricultural or so-called farm tractors are conventional of either two-wheel drive or four-wheel drive types. In the former type, large diameter rear wheels drive the tractor, the operator seat and possibly a cab enclosure for the operator being located generally above the rear axle. In the latter type, both front and rear wheels drive the tractor, the operator cab enclosure being typically centrally located.
Such four-wheel drive tractors are employed for extremely heavy duty service and typically have the engine located in front of the cab, there being a rear mounted lifting hitch extending rearwardly from the tractor for raising or lowering various farm implements designed to be attached to the hitch, such as plows, disc harrows, planters, cultivators and the like.
Such hitches are conventionally a three-point configuration, i.e., have three points of attachment for an implement, the hitch being selectively controllable for being raised or lowered to a desired extent by means of hydraulic power, for example.
THE PRESENT INVENTION IS INTENDED PRIMARILY FOR USE ON SUCH FOUR-WHEEL DRIVE TRACTORS, OWING TO THEIR CONFIGURATION, SIZE AND OTHER FACTORS MORE FULLY EVIDENT FROM THE FOLLOWING DESCRIPTION. However, it is not intended that use of the invention be so limited.
In the use of tractors, regardless of type, having a three-point hitch at the rear, the weight of any apparatus carried behind the hitch such as a plow or other implement carried by the hitch exerts a rearward moment about the rear wheels. In other words the rear wheels act as a fulcrum so that heavy hitch-mounted loads cause the front of the tractor to be very light, possibly adversely affecting the steering. In the case of a four-wheel drive tractor the light loading of the front wheels may prevent them from pulling a full share of the load.
In some cases it is necessary to add weight at the front of the tractor to increase the loading upon the front wheels so as at least to provide for adequate steering.
In the use of tractors of the present type for spraying of herbicides, fertilizers and other liquids, it is now often desired to employ tractor-mounted sprayer tanks having high capacity, for example, 500 gallons. Since the density of spray liquids may approximate ten pounds per gallon, an enormous weight must be borne by the tractor. Hence, concern must be given to weight distribution, particularly when using four-wheel drive tractors, so that all four wheels adequately share in propelling the tractor.
Thus, it is important that the front wheels have sufficient traction. But the mounting of a high capacity spray tank by means of the hitch with the tank center of gravity rearward of the hitch may preclude adequate traction because of the large rearward moment about the rear wheels resulting from a long moment arm and high weight.
In the past, it has been necessary to add weight to the front of the tractor to counterbalance this rearward moment, as by adding additional spray tanks at the front.
Some four-wheel drive tractors are of an articulated type in which the front and rear portions of the tractor are joined by a hinge-like structure as joint located centrally of the tractor. Turning of the tractor is made possible by articulation about this joint. It will be understood that heavy rear-mounted weights, such as a large spray tank carried rearwardly of the hitch, will provide a large bending moment about such joint. This may cause undue strain or wear of the joint and articulation mechanism with consequent damage or shortening of the life of this very expensive type of tractor.
Present arrangements for tractor mounting of spray tanks therefore limit the capacity of the tanks which can be used, require use of additional weights at the front of the tractor, or contribute to problems of the type described.